1. Field of the Invention
The present invention relates to a display apparatus including active elements for driving light emission elements such as EL (electroluminescent) elements and LEDs (light emission diodes) and its driving method, and more particularly to a display apparatus including thin film transistors (TFTs) as active elements and the driving method therefor.
2. Description of the Related Art
TFTs are widely used as active elements for driving an active matrix display such as an organic EL display and a liquid crystal display. FIG. 1 shows a pixel PLi,j in an example of an equivalent circuit of a driving circuit in an organic EL (organic electroluminescent) element (OEL) or an organic light emission diode (OLED) 100.
As illustrated in FIG. 1, the equivalent circuit includes two p-channel TFTs 101 and 102 as active elements and a capacitor (Cs) 104. A scanning line Ws is connected to the gate of the selector TFT 101. A data line Wd is connected to the source of the selector TFT 101. A power supply line Wz for supplying constant supply voltage Vdd is connected to the source of the driver TFT 102. The drain of the selector TFT 101 is connected to the gate of the driver TFT 102. The capacitor 104 is provided between the gate and the source of the driver TFT 102. The anode of the OEL 100 is connected to the drain of the driver TFT 102, and the cathode of the OEL 100 is connected to the ground voltage (or common voltage).
When a selecting pulse is applied to the scanning line Ws, the selector TFT 101 as a switch is turned on and the selector TFT 101 becomes conductive across its source and drain. Simultaneously, data voltage is supplied through the connection between the source and drain of the selector TFT 101 from the data line Wd and accumulated in the capacitor 104. The data voltage accumulated in the capacitor 104 is applied between the gate and source of the driver TFT 102. As a result, drain current Id corresponding to gate-source voltage Vgs of the driver TFT 102 is generated and supplied to the OEL 100, and the OEL 100 having received the drain current Id emits light.
The active matrix display having this structure displays images by supplying data signals corresponding to input video data to the respective pixels PLi,j via the data lines while sequentially applying selecting pulses (scanning pulses) to the respective scanning lines.
However, the known active matrix display holds display data for a period of one frame. This type of display is referred to as a hold-type display apparatus.
When the display continues image display while holding the display data for the frame period, the image display quality, particularly the image display quality of the moving images display, is deteriorated. That is, contours of images are blurred and recognized as blurred images, or false contour noise is generated.
For overcoming these drawbacks, for example, Japanese Patent Applications Kokai No. 2003-223136 and No. 2003-5709 disclose structures for stopping light emission from light emission elements for a predetermined time in a frame period.